• 전기화학회지
• /
• 제15권1호
• /
• pp.19-26
• /
• 2012

표준 전해액에 2중량%의 VC(vinylene carbonate)와 FEC(fluoroethylene carbonate)를 각각 첨가한 전해액으로부터 흑연 음극 표면에 SEI(solid electrolyte interphase) 층을 형성시키고, SEI 특성에 따른 흑연 음극의 저온($-30^{\circ}C$) 충방전 특성을 조사하였다. 흑연의 충 방전 용량은 FEC를 첨가한 전해액, 표준 전해액, 그리고 VC를 첨가한 전해액의 순서로 감소하였고, 충 방시 발생하는 과전압은 반대경향을 보이며 증가하였다. 이는 첨가제의 종류에 따라 생성된 SEI 층의 저항과 전하전달저항에 차이가 있음을 설명하는데, 이를 SEI 층의 화학 조성과 두께를 비교하여 확인하였다. 표준 전해액으로부터 생성된 SEI 층은 C-O 성분을 포함하는 고분자 형태의 화합물과 리튬 염의 환원분해로 생성된 $Li_xPF_yO_z$ 등으로 구성되었다. VC를 포함한 전해액으로부터 생성된 SEI 층은 C-O 화합물 비율이 높고 조밀하여 리튬 염의 분해가 억제되어 얇은 피막이 생성됨에도 불구하고 가장 큰 저항 값을 보였다. 반면에 FEC로부터 생성된 SEI 층은 C-O 성분의 비율이 VC를 첨가한 전해액의 경우보다는 작으면서도 리튬 염의 분해가 크지 않아서, 리튬 이온의 이동이 가장 용이한 피막을 형성하고 있어 가장 낮은 피막저항 및 전하전달 저항을 나타내었다. 결론적으로 FEC를 첨가제로 사용한 경우 생성된 SEI 층의 저항이 가장 작아서 흑연 음극의 저온특성이 가장 우수하였다.

• 대한화학회지
• /
• 제42권6호
• /
• pp.664-671
• /
• 1998

유기 전도성 고분자들중 전도성이 뛰어나고 전기화학적으로 중합이 용이하며 안정성이 뛰어난 피로고분자(ppy)는 산화-환원 활성자리에 회합되는 이온종에 따라서 피막의 형태학적 구조가 다양하다. 그러나 공기중에서 쉽게 노화하며 잘 부서지고 물과 친하지 않은 단점이 있다. 이를 개선하기 위하여 이 다공성 ppy 피막에 높은 개시전위를 갖는 퓨란고분자(pfu)를 끼워심기 중합한 Pt/ppy/pfu(x)전극을 제작하여 그 전기화학적 성질들을 순환전압전류법과 전기호학적 임피던스법으로 조사하였다. 이 때 사용된 도판트 이온은 $PF_6^-,\; BF_4^-$, 그리고 $ClO_4^-$이온 이였으며, pfu의 조성은 ppy에 대하여 0∼1.10 범위였는데 그 조성이 0.1∼0.2의 범위에 있을 때 가장 좋은 산화환원 특징을 나타냈다. 또, $PF_6^-$ 이온이 도우핑되었을 때 전하전달 저항은 다른 이온들로 중합된 것에 비하여 40배정도 낮았으며, 이 중층의 용량은 다른 두 종에 비하여 20배정도 큰 값을 보였다. 전하전달은 주파수의 변화에 영향을 받으며 물질전달에 의한 Warburg 임피던스 항이 포함되는 등가회로를 갖는다.

• Journal of Electrochemical Science and Technology
• /
• 제13권4호
• /
• pp.462-471
• /
• 2022

In this study, the electrochemical impedance characteristics of CO₂/H₂O co-reduction to produce CO/H₂ syngas were investigated in a low-temperature single cell. The effect of the operating conditions on the single-cell performance was evaluated at different feed concentrations and cell voltages, and the corresponding electrochemical impedance spectroscopy (EIS) data were collected and analyzed. The Nyquist plots exhibited two semicircles with separated characteristic frequencies of approximately 1 kHz and tens of Hz. The high-frequency semicircles, which depend only on the catholyte concentration, could be correlated to the charge transfer processes in competitive CO₂ reduction and hydrogen evolution reactions at the cathodes. The EIS characteristics of the CO₂/H₂O co-reduction single cell could be explained by the equivalent circuit suggested in this study. In this circuit, the cathodic mass transfer and anodic charge transfer processes are collectively represented by a parallel combination of resistance and a constant phase element to show low-frequency semicircles. Through nonlinear fitting using the equivalent circuit, the parameters for each electrochemical element, such as polarization resistances for high- and low-frequency processes, could be quantified as functions of feed concentration and cell voltage.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.375.1-375.1
• /
• 2016

Polymerase chain reaction (PCR) has revolutionized genetics and become one of the most popular techniques in modern biological and medical sciences. It can be used not only as an in vitro DNA amplification method but also used in many bioassay applications. The PCR can be used to exponentially produce a large number of DNA copies from a small quantity of DNA molecules in a few hours. However, as unwanted DNA fragments are also often manufactured, the amplification efficiency of PCR is decreased. To overcome this limitation, several nanomaterials have been employed to increase the specificity of the PCR reaction. Recently, graphene has attracted a great interest for its excellent electron transfer, thermal and biocompatibility. Especially, gold nanoparticle-coated graphene oxide (GO/AuNPs) led to enhance electron and thermal transfer rate and low-charge transfer resistance. Therefore, we report the development of a demonstration for the PCR efficiency using a large-scale production of the GO and combination of gold nanoparticles. Because a thermal conductivity is an important factor for improving the PCR efficiency in different DNA polymerases and different size samples. When PCR use GO/AuNPs, the result of transmission electron microscopy and real-time quantitative PCR (qPCR) showed an enhanced PCR efficiency. We have demonstrated that GO/AuNPs would be simply outperformed for enhancing the specificity and efficiency of DNA amplification procedure.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.301.1-301.1
• /
• 2016

We report an ultraclean, cost-effective, and easily scalable method of transferring and patterning large-area graphene using pressure sensitive adhesive films (PSAFs) at room temperature. This simple transfer is enabled by the difference in wettability and adhesion energy of graphene with respect to PSAF and a target substrate. The PSAF transferred graphene is found to be free from residues, and shows excellent charge carrier mobility as high as ${\sim}17,700cm^2/V{\cdot}s$ with less doping compared to the graphene transferred by thermal release tape (TRT) or poly(methyl methacrylate) (PMMA) as well as good uniformity over large areas. In addition, the sheet resistance of graphene transferred by recycled PSAF does not change considerably up to 4 times, which would be advantageous for more cost-effective and environmentally friendly production of large-area graphene films for practical applications.

• Environmental Engineering Research
• /
• 제25권2호
• /
• pp.238-242
• /
• 2020

Sediment microbial fuel cells (SMFCs) illustrated great potential for powering environmental sensors and bioremediation of sediments. In the present study, array anodes for SMFCs were fabricated with graphite rods as anode material and stainless steel plate as electric current collector to make it inconvenient to in situ settle down and not feasible for large-scale application. The results demonstrated that maximum power of 89.4 ㎼ was obtained from three graphite rods, twice of 43.3 ㎼ for two graphite rods. Electrochemical impedance spectroscopy revealed that three graphite rods resulted in anodic resistance of 61.2 Ω, relative to 76.0 Ω of two graphite rods. It was probably caused by the parallel connection of the graphite rods, as well as more biomass which could reduce the charge transfer resistance of the biofilm anode. The presently designed array configuration possesses the advantages of easy to enlarge the surface area, decrease in anodic resistance because of the parallel connection of each graphite rod, and convenience to berry into sediment by gravity. Therefore, the as prepared array node would be an effective method to fabricate large-scale SMFC and make it easy to in situ applicate in natural sediments.

• 공업화학
• /
• 제33권6호
• /
• pp.618-623
• /
• 2022

분리판은 반응물 및 전자를 전달하고 부산물인 물과 열을 배출하며, 막전극접합체의 지지체 역할을 하는 고분자전해질 연료전지의 핵심 구성요소이다. 따라서 분리판의 유로 구조는 연료전지의 성능을 향상시키는데 중요한 역할을 한다. 본 연구에서는 압축률이 다른 구리 폼을 cathode 분리판에 적용한 25 cm² 단위 전지를 이용하여 성능 평가를 수행하였다. 금속 폼의 압축률이 증가할수록 총 저항이 감소하였으며, 특히 전하전달과 물질전달 저항이 사형 유로에 비해 크게 개선되어 중전류밀도 및 고전류밀도 영역에서 전압 손실을 줄일 수 있었다. 가압한 공기를 사용한 사형 유로 구조의 경우 연료전지의 성능이 압축한 금속 폼(S3)을 적용한 유로와 중전류밀도 영역까지는 큰 차이가 없었으나, 고전류밀도 영역에서는 유로 구조의 한계로 낮은 성능을 보였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1996년도 하계학술대회 논문집 C
• /
• pp.1703-1706
• /
• 1996

The purpose of this study is to research and develop polypyrrole(PPy) positive for thin film rechargeable lithium battery. We investigated cyclic voltammetry, AC impedance response and charge/discharge cycling of PPy/SPE/Li cells as a function of temperature. The redox capacity of $PPy/CF_{3}SO_{3}$ film was the most large. The discharge capacity of PPy/SPE/Li cell with $PPy/CF_{3}SO_{3}$ film was higher than those of $PPy/ClO_{4}$ and $PPy/AsF_6$ films at all cycles. The energy density of PPy/SPE/Li cells during 1st cycle was 73, 90 and 101Wh/kg at $25^{\circ}C$, $45^{\circ}C$ and $60^{\circ}C$, respectively. The improvement of energy density is due to reduction of charge-transfer resistance associated doping-undoping process in PPy film with Increasing temperature. $PPy/CF_{3}SO_{3}$ film shows a good property on charge/discharge cycling in PEO-$LiClO_4$-PC-EC electrolyte.

• 한국산학기술학회논문지
• /
• 제13권2호
• /
• pp.510-515
• /
• 2012

본 연구의 목적은 심지구조 유무에 따른 자동차에 적용된 써모사이폰의 저온 작동영역에서의 성능 특성을 고찰하는 것이다. 이를 위하여 작동유체로 물을 사용하는 써모사이폰을 제작하였고, 작동유체의 충진량, 심지 적용 유무, 외기온도 변화 그리고 증발부에 열부량 변화에 따른 성능 특성을 파악하였다, 결과적으로 작동유체의 충진량 40%에서 최적의 열전달 성능을 나타내고, 외기온도 증가에 따라 써모사이폰의 열전달 성능이 증가하였다.

• Journal of Electrochemical Science and Technology
• /
• 제7권2호
• /
• pp.153-160
• /
• 2016

The inhibition ability of N,N-bis(2,4-dihydroxyhydroxybenzaldehyde)-1,3-Propandiimine (DHBP) as a schiff base against the corrosion of API-5L-X65 steel in 1 M HCl solution was evaluated by electrochemical impedance spectroscopy, potentiodynamic polarization and scanning electron microscopy. Electrochemical impedance studies indicated that DHBP inhibited corrosion by blocking the active corrosion sites. The inhibition efficiency increased with increasing inhibitor concentrations. EIS data was analysed to equivalent circuit model and showed that the charge transfer resistance of steel increased with increasing inhibitor concentration whilst the double layer capacitance decreased. The adsorption of this compound obeyed the Langmuir adsorption isotherm. Gibbs free energy of adsorption was calculated and indicated that adsorption occurred through physical and spontaneous process. The corrosion inhibition mechanism was studied by potential of zero charge. Polarization studies indicated that DHBP retards both the cathodic and anodic reactions through adsorption on steel surface. Scanning electron microscopy was used to study the steel surface with and without inhibitor.